An exponential growth in miniaturized smart sensors is imminent in the near future. The rapid growth in technology is bringing the vision of Internet of Things (IoTs) closer to reality at a much faster pace than previously anticipated. This value does not come by connecting every object to the internet but by their intelligent interaction and collaboration. This will open new dimensions of collecting data and extracting information at a scale not possible before. This technology will enable smart cities with improved waste/water management, transportation and lighting, connected cars with smart homes and will revolutionize retail, manufacturing, shopping and healthcare.
The sensor density around a person is expected to increase from a few hundreds to thousands, which will correspond to roughly a trillion networked sensors on the planet. The microsystems encompassing these sensors will have to have high-energy efficiency for computation, communication and sensing operations. This is mainly because many of these microsystems are expected to operate at the edge of the cloud with a battery lifetime of 10+ years, or batteryless operation from harvested energy. This poses new design challenges and opportunities for circuit designers and especially for wireless communication Integrated Circuits (ICs) as they consume a significant amount of power when active in a miniaturized microsystem.
Some efforts are put in place to define an open platform that enables the Internet of Things such as 6LoWPAN-based networks built on the IEEE 802.15.4 standard. Recently, IEEE 802.15.4 compliant radio frequency (RF) front-ends have been reported with exceptional sensitivity (wireless range>100 m) and energy efficiency of 7.2 nJ/bit, 6.8 nJ/bit and 7.4 nJ/bit.
However, there are many IoT applications that only require short-range communication (<10 m), such as wireless proximity sensors for smart meters and parking spaces, home automation within a room, and some wearables for fitness and health monitoring. In these cases, different design tradeoffs can be made in order to improve energy efficiency, as compared to devices that prioritize high performance or ICs designed for worst-case applications. In particular, it is well known that the sensitivity of a receiver directly trades off with its power consumption. Dialing sensitivity back to around −50 dBm could lower the power of the radio significantly and meet the needs of many energy-constrained applications. However, doing so is not trivial, and requires redesigning with focus on ultra-low power from RF front-end through the digital baseband processor.
This disclosure presents a fully integrated 2.4 GHz receiver comprising an RF front-end, analog-to-digital converter (ADCs), and digital baseband processor (DBB) that exploit the relationship of sensitivity and power consumption by adapting the sampling and processing rates of signals in the radio baseband processor. Although not meeting the sensitivity required by the IEEE 802.15.4 standard, this receiver provides a short-range O-QPSK DSSS link that is fully compatible with IEEE 802.15.4 packets. While reference is made throughout this disclosure to a particular standard, it is readily understood that the concepts described herein are applicable more generally to short-range wireless receivers.
This section provides background information related to the present disclosure which is not necessarily prior art.